mk-component-set: apply ld-wrapper for rust-ld

[oxalica]

Upstream-shipped rust-ld is now used as default linker for some targets on nightly. It needs ld-wrapper for interopation with libraries from Nix. Currently wrapBintools interface is uneasy for hook use inside a derivation also containing non-bintools stuff. We hereby copy part of the implementation and wrap rust-ld in-place.

See: rust-lang/rust#71515 (comment)
Fixes #168

External library linking is now working correct. Previously it compiles but the binary fails to run.

$ echo '#[link(name = "crypt")] extern "C" { fn crypt(); } fn main() { dbg!(crypt as unsafe extern "C" fn()); }' >test.rs
$ nix build -f ./repl.nix rust-bin.nightly.2024-05-27.minimal
$ nix-shell -p libxcrypt --run './result/bin/rustc test.rs'
$ ./test
[test.rs:3:13] crypt as unsafe extern "C" fn() = 0x00007f1b90941a40 # address is not deterministic tho

[Nemo157]

I can confirm this works in my test project too. Building with RUSTC_LOG=rustc_codegen_ssa::back::link=info cargo rustc -- -Clink-arg=-Wl,-v I can see in the logs it's using /nix/store/ij8y2zxhbq4ys6d7zrj0iqq0hrm14xdh-rust-minimal-1.80.0-nightly-2024-05-29/lib/rustlib/x86_64-unknown-linux-gnu/bin/gcc-ld/ld.lld as the linker, and the associated rust-lld from there is the wrapped script, and the resulting binary successfully finds its native dependencies.

[DianQK]

Will you port to the upstream rustup? I've submitted a PR (NixOS/nixpkgs#314268), but it only ensures that rust-lld can run. :)

[oxalica]

Will you port to the upstream rustup? I've submitted a PR (NixOS/nixpkgs#314268), but it only ensures that rust-lld can run. :)

Sorry but I think it may be too complicated to handle ld wrapping as a rustup patch, especially with the current wrapBintoolsWith interface. It may also be fragile because of adding more store path dependencies on the wrapped ELF/script, as they cannot be tracked by nix's GC. You can try it if you want to, though.